Ash, Misty, Brock and Pikachu are at the city of Alto-Mare, competing in the annual water races; thereafter Ash meets the legendary Pokémon Latias, who has taken a liking to the young Pokémon trainer. Also in the city are two Team Rocket agents, out to find the ancient, mythical weapon of the city for Giovanni. The weapon is somehow connected with the legendary Pokémon Latias and her brother Latios and the soul dew gem. When Latios is captured and the city is cut off from the outside world, it is up to Ash and his friends to save the city from it own deadly weapon.